Giant topological insulator gap in graphene with 5d adatoms

TL;DR

This paper proposes a new method to create large-gap two-dimensional topological insulators by hybridizing graphene with heavy 5d adatoms like osmium and iridium, enabling robust TI states without Fermi level tuning.

Contribution

It introduces a novel framework for engineering 2D TIs using heavy adatoms on graphene, predicting large gaps exceeding 0.2 eV from first principles calculations.

Findings

Gaps over 0.2 eV predicted for graphene with 5d adatoms

Fermi level tuning not required to achieve TI state

Mechanism is general and applicable to other materials

Abstract

Two-dimensional topological insulators (2D TIs) have been proposed as platforms for many intriguing applications, ranging from spintronics to topological quantum information processing. Realizing this potential will likely be facilitated by the discovery of new, easily manufactured materials in this class. With this goal in mind we introduce a new framework for engineering a 2D TI by hybridizing graphene with impurity bands arising from heavy adatoms possessing partially filled d-shells, in particular osmium and iridium. First principles calculations predict that the gaps generated by this means exceed 0.2 eV over a broad range of adatom coverage; moreover, tuning of the Fermi level is not required to enter the TI state. The mechanism at work is expected to be rather general and may open the door to designing new TI phases in many materials.